Farm animal manure is normally collected in large manure collection containers, for instance, barn collection pits, above-the-ground tanks, in-the-ground tanks and lagoon pits, where it is stored until it is time to spread same onto the fields to act as a fertilizer. It may also be necessary to transfer manure from one container to another. The spreading operation is usually performed by a motorized manure spreader which carries the manure in a tank. Thus, apparatus is required for chopping floating crusts in such containers, for mixing the solid particles with the liquid in order to obtain a suspension, and for pumping manure out of such containers into other containers or manure spreaders.
Farm animal manure consists of solid particles in a liquid, and the solid particles either settle on the bottom of the container (as in the case of pig manure) or form a crust over the liquid (as in the case of cow manure) depending on the density of the solid matter and, in some cases, both conditions obtain. Thus, the mass of manure in the container must be thoroughly mixed prior to pumping in order to maintain the solid particles in suspension, otherwise only the liquid matter will be pumped out while the solid matter accumulates in the container. Moreover, such solid matter tends to clog the pump.
Hitherto, manure handling pumps consisted of a powerful centrifugal pump disposed near the bottom of the container, the impeller turning about a vertical axis, and a conduit system coupled to the outlet of the pump for either circulating manure within the container or away therefrom into a manure spreader or a different container. The conduit system therefore has a first branch leading out of the container toward another container or toward a tank spreader, and a second branch leading to a suitable nozzle pipe for returning into the container the slurry being mixed. A gate controls the selection of conduit branch in order to either agitate the slurry or pump same out of the reservoir. Examples of such centrifugal systems of which many different designs are currently available from farm equipment manufacturers, are described in U.S. Pat. Nos. 3,905,725 dated Sept. 16, 1975 (R. L. Johnson), 3,446,151, May 27, 1969 (H. G. V. Anderson), 3,456,592, July 22, 1969 (L. L. Nelsen) and 3,966,361, June 29, 1976 (B. L. House). Such devices however provide limited efficiency when the reservoir contains a thick floating crust or heavy bottom sediments. Indeed, the mixing capabilities of centrifugal pump systems are at best limited and time consuming, and no agitation takes place during transfer of the slurry to a different container into a tank spreader. Furthermore, clogging of the pump's impeller and consequential loss of pump efficiency remains a serious shortcoming.
It is also known to provide a propeller mixer on a vertical rail mounted to the wall of a container, with means to change the level of the propeller's axis in order to agitate the slurry therein. The mounting structure can be rotated around a vertical axis in order to change the direction of the propeller's axis in a horizontal plane. One such mixer powered by an electric motor and sold under the Trade Mark FLYGT, is manufactured in Sweden by Flygt AB. However, such mixers, although relatively efficient for mixing slurry, when well maintained, are prohibitively expensive to most farms and they are not usable for transferring slurry out of the container. Moreover, in thick manure, it is very difficult to rotate the mounting structure in order to change the direction of the impeller's axis.